Follow - up Observations of the Neptune Mass Transiting Extrasolar Planet HAT - P - 11 b Jason

We have confirmed the existence of the transiting super Neptune extrasolar planet HAT-P-11b. On May 1, 2009 UT the transit of HAT-P-11b was detected at the University of Arizona’s 1.55m Kuiper Telescope with 1.7 millimag rms accuracy. We find a central transit time of Tc = 2454952.92534± 0.00060 BJD; this transit occurred 80 ± 73 seconds sooner than previous measurements (71 orbits in the past) would have predicted. Hence, our transit timing rules out the presence of any large (> 200s) deviations from the ephemeris of Bakos et al. (2009). We obtain a slightly more accurate period of P = 4.8878045± 0.0000043 days. We measure a slightly larger planetary radius of Rp = 0.452 ± 0.020RJ (5.07 ± 0.22R⊕) compared to Bakos and co-workers’ value of 0.422 ± 0.014RJ (4.73 ± 0.16R⊕). Our values confirm that HAT-P-11b is very similar to GJ 436b (the only other known transiting super Neptune) in radius and other bulk properties. Subject headings: planetary systems, stars: individual: HAT-P-11